I wanted to get an outdoor cabinet of some kind on my deck, to hold BBQ tools, charcoal, some garden tools, etc. I looked at Home Depot, but all they had was really ugly molded plastic monstrosities. So, I decided to build one myself.
I wanted to design it using a 3-D CAD package, and I found Google Sketchup was a very cost-effective solution. The cost is “free” (as in beer), and it’s very capable for the money. Constructing the 3-D model is very easy. You can draw with precision in the same sort of way as in real CAD programs. When a line is supposed to intersect a circle at a tangent, or meet the end of another line at right angles, you can be sure it really does.

And you can add “dimension” objects to your model and switch to a parallel projection, to get detailed blueprints to build from. By careful use of layers and the “Scene Manager”, you can have it generate many different blueprints for different parts, from different viewpoints. Dimensioning has some annoying limitations, but it worked out ok.

But what really surprised me about Google Sketchup was the huge volume of free plug-ins and scripts you can add to it. I used a plug-in to give it an approximate ability to add angle dimensions to my blueprints. But the most amazing plug-in I stumbled across is SketchyPhysics. This one adds a complete physics engine to SketchUp, allowing your model to come to life and start moving.

After viewing some videos of what is possible using SketchyPhysics, I thought it would be interesting and educational to try to make the door hinges in my model functional. After installing SketchyPhysics (very easy), the first thing I did, without having done anything special to my model, was just try hitting “Play” on the physics simulation to see what would happen. The result was unexpected, but in retrospect not too surprising:

Conveniently, SketchyPhysics provides a big rectangular block that you can use as a floor for your world. I added one of those for my cabinet to stand on and tried again. This time the result was really interesting:

It was like I had built the entire cabinet, but forgot to use nails!

From what I know about SketchyPhysics now, that result was entirely expected. None of the parts were grouped together. It is entirely not obvious how to make SketchyPhysics do anything useful. I was completely lost, until I discovered Sketchy Physics Tutorial, the Unofficial Guide for those who are Completely Lost. Grouping objects together in SketchyPhysics makes them behave as a single rigid body. To make my door simulation work, the entire cabinet (excluding the doors) would have to be a single group. Each door would be its own group also. And the hinges (carefully modeled on Stanley 4″ tee hinges), would have to be in two parts: the rectangular plates part of the cabinet body group, and the straps part of the door groups. I also learned about how to add the actual physics components (hinges, motors, servos, springs, etc) to the model in a way that the physics engine understands them and can make them come to life. At that point, finally, I had my doors working:

If anybody is interested in building this, here is the complete Sketchup model, and renderings of all the various scenes and views I defined in it.

Since then, I’ve started construction on the actual real-world cabinet. Taking a “money is no object” approach, I chose cedar for the exterior. I bought a bunch of cedar fence boards, which I laboriously turned into ship lap siding using a stacked dado head in my table saw.